1. Field of the Invention
Embodiments of the invention generally relate to optical sensor systems and, more particularly, to improving wavelength stability in broadband source light used to interrogate optical sensors.
2. Description of the Related Art
Optical sensor systems operate by exposing a portion of an optical waveguide to an environmental condition that modulates a light signal transmitted within the optical waveguide. This modulation alters one or more parameters of the light transmitted within the optical waveguide, such as amplitude, power distribution versus frequency/wavelength, phase, or polarization. Analyzing modulated light emerging from the waveguide enables determining values indicative of the environmental condition. Such systems utilize sensors based on, for example, Bragg gratings or interferometers, to measure a wide variety of parameters, such as strain, displacement, velocity, acceleration, flow, corrosion, chemical composition, temperature or pressure. In one example of an optical sensor system, a fiber optic gyroscope (FOG) enables measuring angular rotation since application of force alters the wavelength of light as it travels through a sensing coil of an optical fiber, thereby producing phase changes from which measurements can be made.
Instabilities in a center wavelength of input light provided by a broadband light source may cause variations in sensor response signals produced upon the interrogating light arriving at the optical sensor. For example, broadband sources producing input light without a stable center wavelength when used with a Bragg grating sensor may cause variations in the reflected response signal emitted by the sensor, resulting in incorrect measurements or undesirable noise. In the FOG, the phase change with acceleration depends on wavelength such that any change in the center wavelength of the broadband source input into an interferometer of the FOG produces drifts in a scalar factor associated with the acceleration and wavelength. Accurate and reliable measurements determined by detection of response signals from the optical sensors require a broadband light source outputting light with a center wavelength that does not drift around with time or other environmental changes. However, attempts in many environments to achieve such a stable broadband light source by stabilization and control (e.g., temperature stabilization or vibration dampening) of components proves difficult, expensive and oftentimes insufficient.
Therefore, there exists a need for optical sensing configurations and methods that improve wavelength stability of input broadband light used to interrogate an optical sensor which may include an FOG device.